While the cause of the fire is still being investigated, the Topland charger unit, which was sold at convenience stores in Japan, was subject to a fire hazard recall issued in July that involved some 224,000 units.

The causes of the recharger incidents vary and are being investigated, a spokeswoman for the Consumer Affairs Agency said.

The government-affiliated National Institute of Technology and Evaluation (NITE) recently warned consumers that recharging cables for smartphones and tablets can also dangerously overheat.

NITE has recorded 48 cases in which cables, including micro USB connectors, overheated during a five-year period. Ten cases involved minor injuries to users and in 25 cases there was additional property damage besides the units in question.

“The terminals inside the connectors can become twisted or deformed and interrupt the flow of current,” a spokeswoman for NITE said in explaining one of the causes. “Sweat, liquids and small debris or dust can also cause short circuits and fire.”

The institute has mounted a public awareness campaign telling people not to store cables in dusty, moist areas.

It has also produced videos including one showing a smartphone charging cable that has been intentionally bent at the terminal and then forcibly straightened. It begins to emit smoke when current is applied.